1. Field of the Invention
The present invention relates to an electronically controlled throttle valve unit for controlling opening/closing (opening and/or closing) operation of throttle valves by an actuator such as an electric motor, particularly, capable of operating a throttle on an emergency by opening/closing the throttle valve through throttle operation of a driver when the actuator is in trouble.
2. Related Art
In recent years, conventional carburetor type fuel supply system of the motorcycle has been replaced by that of fuel injection type, which is more highly efficient. At the same time, the conventional mechanical type throttle unit, which transmits a motion of a throttle grip directly to the throttle valve through a control cable, linkage mechanism or the like, has been replaced by that of electronic control system type, called accelerator-by-wire system, in which a throttle operation amount is once detected by a throttle position sensor, and in accordance with the detected amount, a control computer controls the actuator (such as electric motor) to open/close the throttle valve appropriately.
Concerning such an electronically controlled throttle valve unit, if the actuator, throttle position sensor or control computer is out of order, the electronic control of the throttle valve stops, and then, the throttle valve is closed by a link mechanism provided as a fail-safe mechanism. As a result, thereafter, the vehicle cannot be accelerated, and it is difficult for the vehicle to drive for emergency to breakdown lane or to drive to a repair plant, for example.
Then, Japanese Patent Application Laid-Open Publication No. 2-30933 (Patent Publication 1) and Japanese Patent Application Laid-Open Publication No. 5-231188 (Patent Publication 2) disclose an electronically controlled throttle valve, which allows, at a time of being out of order of the vehicle, driving for emergency by enabling to mechanically open/close the throttle valve within a predetermined range of the throttle valve.
In the electronically controlled throttle valve unit disclosed in the Patent Publication 1, a first clutch and a second clutch are provided on both ends of the throttle valve shaft so as to allow connection/disconnection between the throttle valve shaft and the electric motor (actuator) by the first clutch and allow connection/disconnection between the throttle valve and an accelerator pedal (i.e., gas pedal) by the second clutch. At an ordinal normal control by an electric motor, the first clutch is connected and the second clutch is disconnected, and on the centrally, if abnormality occurs in the electric motor, the first clutch is disconnected and the second clutch is connected to thereby enable driving for emergency by pressing a accelerator pedal even if the abnormality occurs.
In the electronically controlled throttle valve unit disclosed in the Patent Publication 2, a one-way clutch is interposed between the throttle valve shaft and the electric motor, and in an abnormal state of the electric motor, the throttle valve is made operative by disconnecting the throttle valve shaft from the electric motor. A first lever and a second lever are disposed on a side opposite to the electric motor with respect to the throttle valve in a manner such that the first lever is supported on a throttle valve shaft rotatably to be freely swingable by a accelerator pedal cable, and on the other hand, the second lever is provided on the throttle valve shaft rotatably therewith. By interposing a coil spring between the first lever and the second lever, pressing or urging forces are generated in relatively opposite directions to each other.
When the electric motor is out of order and in trouble, the first lever swings corresponding to an operation of the accelerator pedal, a rotation is transmitted through the coil spring to the second lever and then throttle valve shaft is rotated to open the throttle valve. Further, with the structure in which an engaging piece of the second lever is engaged with one side of the first lever, when an operation is performed to close the accelerator pedal, the rotation of the first lever is transmitted to the second lever by the engaging piece and the throttle valve shaft is rotated in a direction of closing the throttle valve.
However, in the electronically controlled throttle valve unit disclosed in the Patent Publication 1, when the actuator is in trouble, connection/disconnection of the first clutch and the second clutch need to be executed, and accordingly, it is necessary to cope with an abnormality in the clutch control system. Therefore, it is hard to say that such electronically controlled throttle valve unit is excellent in certainty and reliability of driving for emergency.
In addition, in the electronically controlled throttle valve unit disclosed in the Patent Publication 2, since the throttle valve shaft is operated in a direction of opening the valve through the coil spring interposed between the first lever and the second lever, there is a fear that a desired valve opening amount may not be achieved due to aging of the coil spring.
Furthermore, the electronically controlled throttle valve units of the Patent Publications 1 and 2 have such a defect that the number of their components is increased, and hence, their structure is made complicated, thus increasing manufacturing cost and easily inducing troubles.